Regulated electric power supply device



Sept. 3, 1963 B. G. MAGNUSSON 3,

REGULATED ELECTRIC POWER SUPPLY DEVICE Filed July 9, 1959 3 Sheets-Sheet 1 Sept. 3, 1963 B. e. MAGNUSSON 7 REGULATED ELECTRIC POWER SUPPLY DEVICE Filed July 9, 1959 5 Sheets-Sheet 2 IN V EN TOR. 5w fir! %wwsw United States Patent The presentinvention relates to an electric power supply device for deriving a direct voltage from an alternating voltage source, said direct voltage being substantially constant and independent of variations in the load and the voltage-0f the alternating voltage: source.

The power supply device comprises-arectifier device which is adapted to be fed from the alternating voltage source, anda smoothing filter in the fQIITLDf a tour-terminal network connected between the, output of the rectifier device and terminals to which the load is to be connected. According to the invention the device further comprises a transistor, an additional-rectifier device, in the following called auxiliary rectifier device, which is also adapted to be fed from the alternating voltage source, a direct voltage source delivers ac-onstan-t referencevoltage, and a summation circuit. The transistor is connectedin series with the output circuitof the firstrn-entioned rectifier device. The summation circuit is" arranged to sum up voltage across-theload, the said reference voltage and the output voltage from the auxiliary rectifier device. Theoutput voltage front the summation circuit is applied to the transistor as control voltage. Thiscont-rpl voltage is such that the transistor effectively blocks the load; current duringa certain part of each If the load or the.

half-cycle of the alternating voltage. R.M. S.; value of thealternating voltagevaries, the said control voltage changes so that the time during which the transistor blocks the load current is. decreased or increased, whereby the average value of the load direct current is increased or decreased respectively so that. the voltage across the load remains substantially unchanged. Thus, the transistor serves as a switch which breaks and closes the load circuit at times determined by the control voltage.

The invention will beydescribed more in particular inconjunction with theaccornpanying drawings.

FIGURE 1 shows a circuit; diagram of a powersupply device accordingto theinvention. I

. FIGURES 2 and 3 show difierent embodirnentsot the smoothing filter included in the device.

FIGURE 4 shows the circuit diagram of an embodi mentof the invention.

FIGURES 5 to 8 are graphs showing currents v and voltages as functions of time in difierent embodiments of the invention.

In FIGURE '1 T designates a transformerhaving a primary winding? andtwo secondary windings S1 and 52.; Two rectifier diodes D1 and D2 are connected to the secondary winding S1 to form a full wave rectifier.

From. this. rectifier the desired DC. power is applied to theload which isrepresented by a resistor RB, in. the figure. LP is a low pass filter tor smoothing the voltage delivered by the rectifier Dl-,--D2. The filter LP may be designed as shown in FIGURE 2 or FIGURE 3. In both, cases the shunt branch of the. filter consists of a capacitor C. The series branch of the filter consists in FIGURE 2 of a choke L and inEIGURE 3 of aresistor R,

A power transistor Q is connected with its emitter and collector in series with the load circuit of the rectifier Dt-nz. ContrO ag r e rans sto- Q. is ake from the summationcircuit S, is amplifiedin a DC. amplifier Fsand. applied. to thetransistor between its base and emitter. To the summation circuit S'are connected direct voltage source ,E,and a rectifier. consisting of diodes D4 and D5 which are connected .tojthe secondary winding 82 of the transformer and tform the'said -auyiil iary rectifier device. The direct voltage so]urc': lEl sup plies a constant reference voltage and. preferably consists Iota Zener. diode connected to ,an ordinary D.C. source (not shown) which drives-a current through thezener diode which inturn has such characteristics that the voltagedrop across it becomes constant and withinwide limits, is indep end ent of the currentthrough it. i

The summation circuit S consists of circuit elements so interconnected that its output voltage which isto control the transistor Q, becomes equal to the algebraic sum of the direct voltage across the load RB,1 the reference voltage from source -'E and. the. pulsating direct voltage from rectifier D4-D5, The .rneans for producing the control voltage are .sodimensioned that the ,conti ol voltageduring each half cycle of the alternating voltage varies between positive and negative values whereby the transistor, will be, conductive to the load current during a part of each half cycIe and :block the load current during another part of each half-cycle. v i i If the filter 'LP is designed as .shownin FIGURE 2,

thatis, has a choke in its series branch, a diode D3 should I be, shunted.acrosstheinputfot filterto maintain the. 0on tinuity of the direct current through the chokewhen transistor Q breaks the loadcurrent. Diode D3 is not needed if the. series branch'of, the filter is a pure resistance as shownin FIGURE 3. i

Theamplifier F may be an electr-ontube or transistor amplifier of known 7 type which obtains the required operating power from rectifiers connected to additional windings. (not shown) on transformer. T.

In the embodiment according toy-FIGURE, 4 the smoothing lfilter consists of a resistor R and a capacitor C. Thesurmnation circuitbene comprises a resist-or, R1

which isvconnected across output of the rectifier 13437-135,- Nq amplifier torthe control voltageotthe, transistor has. beentshowninPlGURE 4, course an amplifier may be provided in this en bodirnent also.

half of winding S1 e -absolute value ofaalternating voltage across either halfof winding S2 I U control, voltage lbe'tween the base and emitter of transistor Q i I i -bas-e current of transistonQ z' collector current of transistor Q fl ile cgth of the collector current pulses (current an- The diagrarn of FIGURE. 5 illustrates the mode of op-. eration ofrthe embodiment shown FIGURE}. The. capacitor,, C has a capacitywhich is solargethatthe alter-f nating voltage across it,can .befneglect'edi. E is larger than I U. The, control voltage. U}, becomes." equal to U.E.+.the. voltage drop .across ..R1.' Atthe' tiin =0;- when the. alternating voltage changes polarity, th base. of thetransistor is at a negative potential with respect to. the emitter, anda. certainv base current is. then flowing: whichrnakes the transistonconductive. As long as e} ethar U odes Dian- 121a lss s id, ere: f re .BQHQFWI u ren can a u i his t va Patented. Sept. 3, 196a e s awash. in t e ia mshaveth o begin to decrease.

, reversed order.

. current.

' When e has reacheda value equal to U at time 13' collector current begins to flow. The base current passes through resistor R1 and causes a voltage drop in this resistor which keeps the diodes D4 and D5 blocked until the voltage e has become equal to this voltage drop. This occurs at time 2 and up to this time the voltage U is substantially constant. At time t U begins to change in a positive sense, wherebythe'base current and the collector current,

At time t U passes through zero, and, the transistor is then cutoff and remains in this condition till time 1., when U passes through zero again and becomes negative. The process is now repeated but in the Thus, for each "half-cycle of the alternating voltage two current pulses are obtained in the collector circuit of the transistor, and the load current through RB. becomes substantially equal to the time average value of the collector Obviously the average value becomes dependent on current angle If the load RB is'changed, the voltage U will also change somewhat. Hereby the points 11 and t will be dis- "placed with i respect to each other so that the current angle 0 decreases if U increases and increases if U decreases. Hence a change of the current through the load is effected, and this change in the current is suchthat the change in the voltage is compensated for to an extent which is larger the larger current gain the transistor has. In order that a satisfactory stabilization shall be obtained the maximum value of e should be much less than E so that a very small change in U causes a large change I of 6 If the ratio of collector current to base voltage (transconductance i /U is very large, E needs only be slightly larger than U. In such case, however, the

capacity of capacitor C must be sufiiciently large so that the maximum value of the ripple across thecapacitor does not become too large in relation to the maximum ampli-' tude of voltage e If the voltage of the alternating voltage source connected to the primary of transformer T is changed, the voltages e ande are changed correspondingly. Hereby the points t and t are displaced in the same direction,

but since e is [always flatter than e the time t will be displaced more than time t Thus even in this case a change in the current angle 0,, occurs whereby the change in the voltage across the load is compensated for.

FIGURE 6 shows voltage and current diagrams for an embodiment of the invention which differs from that shown in'CFIGURE 4 in that the rectifier diodes D4 and D5 are connected with the forward direction opposite to that shown in FIGURE 4. In this case the voltage E is less than U. Thus, the control voltage U, at the base of transistor Q now becomes equal to U-Ee U5 is positive as long as e is less than U-E, and transistor Q is then blocked, Between times t and t U becomes negative, and the transistor then becomes conductive. It will be easily realized that in this case also a change in the load will cause a change in the current angle 9 so that the change in the voltage across the load is opposed.

FIGURE 7 shows voltage and current diagrams for an embodiment of the invention in which the smoothing I filter has a choke in the series branch and a diode (D3 in FIGURE '1) connected across the input of the filter.

In other respects this embodiment agrees to that shown in FIGURE 4. I The base voltage U and the base current i of transistor Q here vary in the same manner as shown'in FIGURE 5. Collector current i however, will now flow] as long as base current flows. This is due to the influence of the filter. choke which, because of its inductance, opposes any change in the current therethrough. 'When the basecurrent has dropped to zero and the transistor is consequently blocked, the choke drives current through the diode shunted iacross the input of the filter. The voltage across the input of the filter follows voltage e till time t and then drops to practically zeroand remains at this value till the transistor begins 4 to conduct again. The direct voltage after filtering in the L-C-filter becomes equal to the time average value of this input voltage. v

FIGURE 8 shows voltage and current diagrams for an embodiment of the invention in which the smoothing filter has a choke in the series branch and a diode D3 connected across the input of the filter, and in which the diodes D4 and D5 are connected with their forward interrupts andcloses the load circuit.

- possible to control load powerswhich are considerably direction opposite to that shown in FIGURE 4. This diagram resembles the diagram of FIGURE 6, but the collector current has here a wave shape different from that shown in FIGURE 6 due to the effect of the choke.

Transistor Q will operate as a contact which alternately Therefore it is larger than the loss power of the transistor, since the tran sistor when conducting takes up only a small voltage drop and when blocked passes only a very small leakage current. The etficiency of the power supply device is primarily determined by the losses'in the transformer windings and in the series branch of filter LP. If the series branch is a resistor ("R in FIGURES 2 and 4),

' the losses may amount to 10- to 910% of the load power.

The efficiency is improved if the filter has a choke (L, in FIGURE 3) instead of .a resistor in the series branch, 7 I

because the resistance of the choke can be made small and the wave shape of the collector current is improved. While the transistor Q is represented in FIGURES l and 4 by the symbol indicating a transistor of the p-n-p type, a transistor of the n-p-n type can of course be used as well, provided that the and diodes are reversed.

The transistor Q may also be of the p-n-p-n type which I has a characteristic similar to that of the thyratron, that said alternating voltage source; an output circuit for said rectifying means including filter means and output terminals for connecting a load to the device; a transistor having a plurality of electrodes, one being a control electrode;rneans connecting said transistor in series with I said output circuit; a reference voltage source for producing a substantially constant reference voltage; means for deriving from said alternating voltage source a pulsating voltage with a wave-shape having sloping parts; a

controlcircu-it extending between a control electrode and another electrode of said transistor; said control circuit including said reference voltage source, said output terminals and means for applying said pulsating voltage in series into said circuit; said reference voltage having such 7 polarity and magnitude in relation to the desired voltage across said output terminals that the resulting voltage between said control electrode and said other electrode of the transistor changes polarity during each pulsation of said pulsating voltage, thereby causing collector-emit ter current path through the transistor to be alternately cut off and conductive. g

2. The power supply device as claimed in claim 1 in which'said filter means consists of a four-terminal network having a resistor in a series branch and a capacitor i in a shunt branch. 3. The power supply device as claimed in claim 1 in which said filter means consists of a four terminal net-- work having a choke in a series branch and a capacitor in a shunt branch, and in which a rectifier is connected across the input terminals of the four-terminal network.

4. The power supply device as claimed in claim 1 wherein the magnitude of the reference voltage is less polarities of the DC. source than the magnitude of said stabilized direct voltage, and the polarity of the reference voltage is the same as the polarity of said pulsating voltage.

5. The power supply device as claimed in clairnl wherein the magnitude of the reference voltage is larger than the magnitude of said stabilized direct voltage, and the polarity of the reference voltage is the opposite from the polarity of said pulsating voltage.

6. A power supply device for deriving astabilize direct voltage from an alternating voltage source, comprising: first rectifying means connected to said alternating voltage source; filter means for smoothing the output voltage from said first rectifying means; direct v the difference between the direct voltage across said output terminals and said reference voltage; and means for applying said varying voltage to control said transistor to cause the transistor to be alternately cut olf and made conductive at the times for polarity changes of said varying voltage. v

7. A power supply device for deriving a stabilized direct voltage from an alternating current source, comprising in combination: firstrectifying means connected said first rectifying means including filter means and output terminals for connecting a load to the device; a transistor including base, emitter and collector electrodes and having its collector-emitter current path connected in series with said output circuit; a control circuit extending between the base electrode and one of the other electrodesv of said transistor, said control circuit includ ing in series combination said output terminals and resistance means and a source of substantially constant reference voltage; and second rectifying means connected to said alternating voltage source and having its output connected to said resistance means to produce a pulsating voltage across said resistance means; said reference voltage having such a polarity and magnitude in relation to the voltage across said output terminals that the resulting voltage between the base and said other electrode of the transistor changes polarity during each half cycle of said alternating voltage thereby causing the collectoremitter current path of the transistor to become alter- References Cited in the file of this patent UNITED STATES PATENTS 2,815,479 Rechnitzer Dec. 33,1957 2,886,761 Rabier May 12, 1959 2,936,413 Searcy May 10, 1960 Harrison June 12, 1960' 

1. A POWER SUPPLY DEVICE FOR DERIVING A STABILIZED DIRECT VOLTAGE FROM AN ALTERNATING VOLTAGE SOURCE, COMPRISING IN COMBINATION: RECTIFYING MEANS CONNECTED TO SAID ALTERNATING VOLTAGE SOURCE; AN OUTPUT CIRCUIT FOR SAID RECTIFYING MEANS INCLUDING FILTER MEANS AND OUTPUT TERMINALS FOR CONNECTING A LOAD TO THE DEVICE; A TRANSISTOR HAVING A PLURALITY OF ELECTRODES, ONE BEING A CONTROL ELECTRODE; MEANS CONNECTING SAID TRANSISTOR IN SERIES WITH SAID OUTPUT CIRCUIT; A REFERENCE VOLTAGE SOURCE FOR PRODUCING A SUBSTANTIALLY CONSTANT REFERENCE VOLTAGE; MEANS FOR DERIVING FROM SAID ALTERNATING VOLTAGE SOURCE A PULSATING VOLTAGE WITH A WAVE-SHAPE HAVING SLOPING PARTS; A CONTROL CIRCUIT EXTENDING BETWEEN A CONTROL ELECTRODE AND ANOTHER ELECTRODE OF SAID TRANSISTOR; SAID CONTROL CIRCUIT INCLUDING SAID REFERENCE VOLTAGE SOURCE, SAID OUTPUT TERMINALS AND MEANS FOR APPLYING SAID PULSATING VOLTAGE IN SERIES INTO SAID CIRCUIT; SAID REFERENCE VOLTAGE HAVING SUCH POLARITY AND MAGNITUDE IN RELATION TO THE DESIRED VOLTAGE ACROSS SAID OUTPUT TERMINALS THAT THE RESULTING VOLTAGE BETWEEN SAID CONTROL ELECTRODE AND SAID OTHER ELECTRODE OF THE TRANSISTOR CHANGES POLARITY DURING EACH PULSATION OF SAID PULSATING VOLTAGE, THEREBY CAUSING COLLECTOR-EMITTER CURRENT PATH THROUGH THE TRANSISTOR TO BE ALTERNATELY CUT OFF AND CONDUCTIVE. 